Puerto Rican drug users have been over-represented among AIDS cases in the U.S. since early in the epidemic. Significant differences in risk behaviors have been identified between Puerto Rican drug users (injectors and crack smokers) who reside on the island of Puerto Rico and those who reside in New York, but little information exists to help understand these differences. The mobility and migration of Puerto Ricans between New York and Puerto Rico provides a unique opportunity to examine the impact of diverse sociocultural environments on risk behaviors in a single ethnic group. The proposed project will study Puerto Rican drug injectors and crack smokers in Bayamon, Puerto Rico and East Harlem, New York- communities with high rates of HIV/AIDS among drug users. Its primary aims are to: (l) examine the contribution of Predisposing, Enabling, and Reinforcing factors, as defined by the PRECEDE model; within the domains of psychological, social, health-related, cultural and environmental influences on drug and sex-related risk behaviors; (2) assess the impact of these determinants on changes in risk behavior over a 12-month period; (3) assess whether the determinants of risk behavior and risk behavior change are moderated by migration, residency, acculturation and mobility patterns; (4) assess whether the determinants of risk behavior and risk behavior change are moderated by serostatus; and (5) develop recommendations for tailored interventions. The PRECEDE theoretical framework will be used as a heuristic device to develop models to predict current risk behaviors, and changes in risk behaviors over time; and to identify intervention points. Qualitative and survey methods will be used. Data will be collected from three samples: (l) Island-dwelling Puerto Ricans; (2) New York Puerto Ricans born in the US; and (3) New York Puerto Ricans born on the Island. Linear and logistic regression techniques will be used to assess relationships between the potential determinants and both current risk behaviors and risk behavior changes.